The present disclosure refers to a ring rolling method for producing a contoured ring rolling product. The disclosure also refers to a rotating jet engine component made of a nickel-based alloy, which is produced by this method.
Ring rolling is a hot forming method used as an alternative to forging for producing rings, including contoured rings. While in forging a blank previously heated to forging temperature is brought into its desired shape inside a form by hot forming, in ring rolling a previously heated ring blank is rolled into the desired shape by one or more rolling steps. With respect to the forging process, ring rolling is considered to be much more flexible in terms of ring rolling products to be formed with a ring rolling machine. For contoured ring rolling, radial-axial rolling units are often used. In such ring rolling machines, both the ring height and the ring wall thickness are simultaneously reduced in one rolling step, in particular by introducing the respective desired contour. In order to obtain the desired ring rolled end product from a ring blank, it is normally required to perform the ring rolling process in multiple steps. Between each ring rolling step, the ring blank is heated again or reheated.
Each ring rolling machine is provided with a control device for controlling the rolling process. The control device monitors determined process parameters, such as the ring growing rate, the axial and radial rolling force, or the temperature of the rolled blank during the rolling process. In this control, a value is respectively set with respect to the respective process parameters. Due to tolerances in the geometry of the respective ring blank and the behavior of the same during rolling, errors in the ring geometry and/or in the texture of the finished ring rolled product may occur. Thus, ring rolling is not considered to have sufficient process safety for components with strict requirements. Thus, it is not used or it is only used as a preparatory step for the subsequent form forging step in such applications, where the ring rolled product has to be provided with tight tolerance limits and has to be reproducibly produced within these tolerance constraints. Components rotating at high speeds, such as components of jet plane or gas turbines, have to fulfill high requirements of the property profile of formed products. For this reason, such components, such as jet engine disks or the like, are formed by forging from a forged blank. Due to the small number of process parameters compared to ring rolling, parts—in particular parts having to fulfill high requirements at strict tolerance limits—may be produced by forging in a reproducible way, thus not including a manual intervention. Due to incremental forming in the axial and radial rolling gap and due to feedback control implemented in control of the rolling unit, the deformation is not constant across the circumference of the rolled ring. This can lead to an inhomogeneous circumferential structure of the ring, which may provide inhomogeneous properties of the disk of the engine. In case of large deviations of the monitored process parameters, it may be necessary to manually intervene in the ring rolling process. Moreover, it may not be assessed, if the ring rolled products actually fulfill the respective requirements. For this reason and due to the possible necessity of a manual intervention, ring rolled products, which have to be produced within tight tolerance limits, cannot be considered to be sufficiently reproducible.
Even when such high load rotating parts, such as turbine disks, may be reproducibly produced by swaging from a nickel-based alloy, certain drawbacks have to be taken into account. One drawback is the unavoidable burr on the forged product caused by forging, which has to be removed after the forming process. This requires a further processing step. The typical material used for such parts, such as a nickel-based alloy, is relatively expensive. The inevitable burr caused by forging which has to be subsequently removed thus requires a higher material use with respect to the forged product. Moreover, due to the required shape of the swaged product, a frequent drawback consists in that the structure of the forged products does not comply, in some areas, with requirements regarding a fine granularity, since in these areas rough grains are found, despite the forming. This can only be overcome by material thickening, which however is to be avoided.
The foregoing examples of the related art and limitations therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.